The role of unawareness on functional status in mild Alzheimer's dementia

Alzheimer's dementia (AD) is characterized by a progressive decline in memory in addition to decline in at least one other cognitive domain. Integral to the diagnosis is a simultaneous decline in functional abilities such as driving skills, and often an unawareness of this decline. Individuals who are unaware of deficits are often unable to accept the help that they need in completing functional tasks and may put themselves in dangerous situations. For example, individuals with an unawareness of their own deficits may prolong driving cessation. Cognitive status explains some, but not all, of the variability in functional abilities. This study examined the relationship between cognition, unawareness, and functional ability in individuals with mild AD as well as in healthy older adults. Understanding this relationship in healthy older adults will help to establish a baseline prior to disease onset. This baseline is not well understood thereby potentially compromising the safety of even healthy older adults. For example, current driving laws with older adults rely on the assumption that individuals will be able to regulate their driving behaviors as they become aware of age-related changes. This study used a virtual reality driving simulator (VRDS) to assess driving performance in healthy controls with exploratory analyses conducted on individuals with mild AD. Awareness was measured by participant-reliable informant discrepancy scores on the Instrumental Activities of Daily Living (IADL) Questionnaire, as well as discrepancy scores between the participant's perception of performance on the VRDS versus actual performance. Results with healthy controls established no relationship between functional ability and awareness when holding performance on cognitive testing constant. Instead, a relationship was found between functional ability, as measured by the IADL questionnaire, and awareness of functional ability in healthy older adults (r= -.747, p<.01). As functional ability decreased, awareness of functioning also decreased suggesting that those individuals with greater functional impairments are less aware of such impairments and therefore pose a safety risk. The MMSE was also linked to functional ability in healthy controls, as measured by the IADL, suggesting a relationship continuum between global cognitive status and functioning in healthy older adults from the community. Additionally, trends in the data for individuals with mild AD suggest a correlation between global cognitive status, as measured by the MMSE, and measures of awareness on both functional measures. Findings suggest that unawareness can lead to increased safety risks in healthy older adults. Measurement tools such as the IADL and MMSE may serve to identify those individuals at risk for both healthy older adults as well as individuals with mild AD.